It is well known to provide one or more sets of characters in a printer arrangement in which incoming signals identify characters to be printed. The character sets perform a translation function by providing to the printer the appropriate raster patterns or other modulation bits in response to incoming commands to print particular characters so that the actual imaging apparatus of the printer can effect the physical printing of the characters.
A difficulty which commonly plagues printer systems is that of storage capacity for the character sets. Depending upon printer resolution and other factors a large number of bits may have to be stored for each character. If the additional requirement for storing several different sets of characters is imposed, an even greater storage burden is placed upon the system. Moreover, certain types of characters such as Chinese characters are relatively complex and typically require relatively large storage capacities, particularly if enough data is to be stored to provide for printed characters of high resolution.
Various techniques have been employed in an attempt to reduce the storage capacity required in various printer systems. A common technique is to compress the bit stream for purposes of storage of the characters with the compressed data being thereafter decompressed prior to use. An example of compression is provided by U.S. Pat. No. 3,987,412 of Thomas Harvey Morrin, entitled Method and Apparatus for Image Data Compression Utilizing Boundary Following of the Exterior and Interior Borders of Objects, issued Oct. 19, 1976 and commonly assigned with the present application. The arrangement shown in the Morrin patent provides compression by virtue of the format the data is presented in for purposes of printing. Morrin discloses a border-following scheme in which as each dot of a character is printed the printer then vectors directly to the nearest dot which is the next to be printed.
Arrangements such as that described in the Morrin patent are generally useful in reducing the required storage space in printers having various different types of characters and character sets. Over and above those considerations, it is desirable to further save on storage space where complex characters are used. This is particularly true, for example, in the case of Chinese characters and like oriental characters which tend to be relatively complex in terms of the bit patterns that must be stored to print them. The problem is particularly severe where high resolution requirements are imposed.
One example of an arrangement for reducing the storage capacity required by oriental characters is described in a publication by Shen et al, "Interactive Ideographic System", IBM Technical Disclosure Bulletin, Vol. 17, pp. 2024-2027, December 1974. Another example is provided by Hasegawa in Japanese Patent Application publication No. 49/129947 and is entitled "Character Generating System". Hasegawa describes a system for composing characters by combining certain elementary symbols in different relative positions and in different proportions. While such arrangement provides certain advantages, it has been found that problems frequently arise in determining the exact positions of the stored symbols and the proportional sizes thereof during the printing process. Similar comments apply to the arrangement described in the publication to Shen et al. Further examples are provided by U.S. Pat. No. 3,852,720 of Park, "Method and Apparatus For Automatically Generating Korean Character Fonts", issued Dec. 3, 1974, and U.S. Pat. No. 3,999,167 of Ito et al, "Method And Apparatus For Generating Character Patterns", issued Dec. 21, 1976.
While arrangements of the prior art have recognized that storage capacity can be reduced in the case of Chinese or like oriental characters by dividing the characters into components for purposes of storage with the components later being combined during the printing process, they have created various other problems, particularly in the manner in which the character components must be recombined if reasonable resolution is to be achieved.